From: Ravi Bangoria Date: Fri, 23 May 2025 22:21:55 +0000 (-0700) Subject: perf mem: Describe overhead calculation in brief X-Git-Tag: v6.16-rc1~57^2~8 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=00a23c000e13d4c66f38eefd530dc377cc90ec14;p=thirdparty%2Flinux.git perf mem: Describe overhead calculation in brief Unlike perf-report which uses sample period for overhead calculation, perf-mem overhead is calculated using sample weight. Describe perf-mem overhead calculation method in it's man page. Reviewed-by: Leo Yan Signed-off-by: Ravi Bangoria Cc: Adrian Hunter Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Kan Liang Cc: Peter Zijlstra Cc: Stephane Eranian Link: https://lore.kernel.org/r/20250523222157.1259998-1-namhyung@kernel.org Signed-off-by: Namhyung Kim Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/Documentation/perf-mem.txt b/tools/perf/Documentation/perf-mem.txt index a9e3c71a22055..965e73d377724 100644 --- a/tools/perf/Documentation/perf-mem.txt +++ b/tools/perf/Documentation/perf-mem.txt @@ -137,6 +137,25 @@ REPORT OPTIONS In addition, for report all perf report options are valid, and for record all perf record options. +OVERHEAD CALCULATION +-------------------- +Unlike linkperf:perf-report[1], which calculates overhead from the actual +sample period, perf-mem overhead is calculated using sample weight. E.g. +there are two samples in perf.data file, both with the same sample period, +but one sample with weight 180 and the other with weight 20: + + $ perf script -F period,data_src,weight,ip,sym + 100000 629080842 |OP LOAD|LVL L3 hit|... 20 7e69b93ca524 strcmp + 100000 1a29081042 |OP LOAD|LVL RAM hit|... 180 ffffffff82429168 memcpy + + $ perf report -F overhead,symbol + 50% [.] strcmp + 50% [k] memcpy + + $ perf mem report -F overhead,symbol + 90% [k] memcpy + 10% [.] strcmp + SEE ALSO -------- linkperf:perf-record[1], linkperf:perf-report[1], linkperf:perf-arm-spe[1]